1). Field of the Invention
This invention relates to an apparatus for electrical testing of a substrate having a plurality of terminals.
2). Discussion of Related Art
Substrates such as wafers or other arrays of packaged electronics devices often have active circuits formed within them. Terminals are formed on the substrates to which electrical contact can be made for purposes of testing the circuits before final assembly. Probe cards are used for making electrical contact with the terminals. A probe card includes a plurality of probes which are brought into contact with the terminals. An electrical tester is connected to the probes. Electrical signals can be transmitted from the electrical tester thorough the probes and the terminals to the electrical circuits, or signals can be sent from the circuits through the terminals and probes to the electrical tester.
In order to make proper contact between the probes and the terminals, the substrate and terminals have to be brought into alignment with one another both rotationally and positionally, and then be moved closer to one another. A force has been exercised between the probe card and the substrate to ensure proper contact between contact regions of the probes and the terminals.
FIG. 4 illustrates one apparatus that can be used for aligning and probing of a substrate includes a frame 110, a probe card 112, a horizontal alignment stage 114, and a vertical translation stage 116. The probe card 112 is secured in the top of the frame 110. The alignment stage 114 is located on the base of the frame 110 and the translation stage 116 is located on the alignment stage 114. The alignment stage 114 can be moved in horizontal directions and the translation stage 116 can be moved relative to the alignment stage 114 in a vertical direction. The translation stage 116 generally includes a screw 118 with a holder 120 located on top of the screw 118 for securing a substrate to.
A problem with the apparatus of FIG. 4 is that the screw 118 moves together with the alignment stage 114 in horizontal directions. A center axis of the screw 118 is thus movable relative to a center point of the probe card 112. When the translation stage 116 is moved in an upwardly direction so that the substrate makes contact with the probe card 112, a moment 122 is created because of misalignment of a force created by the probe card 112 with respect to a center axis of the screw 118. The moment 122 has a tendency to topple the translation stage. As a consequence, the screw 118 has to be of a relatively bulky design to be able to counteract the moment that is created.
According to one aspect of the invention apparatus is provided for electrical testing of a substrate having a plurality of terminals. The apparatus includes a frame, a probe card, a translation device, an alignment device, and a holder. The probe card includes a probe card backing member and a plurality of probes extending from the probe card backing member and is secured to the frame. The translation device is secured to the frame. The alignment device is located on the translation device. The holder is capable of holding a substrate and is secured to the alignment device. The alignment device is operable to cause alignment movement of the holder past the probe card so that selected ones of the terminals are brought into alignment with selected ones of the probes. The translation device is operable to cause translational movement, transverse to the alignment movement, of the alignment device with the holder towards the probe card. A respective one of the terminals is so brought into contact with a respective contact region of a respective one of the probes.